Manufacture of motor fuels



May 3, 1938,. J. c. MoRRELL MANCTURE oF MOTOR FUELS Filed Jan. 2.9, 193ecle ffrell,

Patented May 3, 1938 gases produced, for example, in cracking a topped e crude with the primary object of producing gasoline may run as high as 10% by weight of the charging oil under intensive cracking conditions. 'I'he composition of these gases will vary with the severity of the cracking operation, ,the nature of the charging stock, the phase prevalent during o the operation, and other factors, The following table shows a list o! the hydrocarbon compounds which have been found in the fixed gases from oil cracking plants: 'Hydrogen H2, methane CH4, ethane CzHe, ethylene 02H4, propane Cal-Is, propylene 03H5, butanes (normal and iso) Cil-11n, and butenes (normal and iso) C4Hs. l The above tabulation omits mention of minor constituents such as hydrogen sulphide, low boiling mercaptans, and morehighly unsaturated hydrocarbons than the mono-olens, such as, for example, butadienes, but it will serve to indicate the general character o! some of the gas mixtures which maybe treated by the'present process.

Intensive researches have been conducted to Y 35 'find a practical method for augmentingthe supply of cracked gasolineb'y forming liquid polymers from the gaseous olens present in cracked hydrocarbon gas mixtures. Fortunately, ,all of the dimers and manyof the trimers and mixed 40 polymers-of the normally gaseous mono-oleiins boil within the range of commercial motor fuel iand are characterized by a satisfactory stability and particularly by a good antiknock value, which generally exceeds that of any oi' the components 45 of cracked gasoline. For purposes of reference the following table is introduced to show the boiling ranges of the dimers of the lower boiling l mono-oleilns:

Boiling points oi olcn dimers Y I F. Hexylene- 155 Octyleue- 255 55 Dacylene. A* 323 Dodecylene 417 The tendency of* the gaseous'mouo-olens to polymerize varies considerably'when using diiier- 60 ent catalysts and also with the same catalyst.

l 2,116,157 UNITED sTATEs PATENT oFFlcEf- 2,116,157 MANUFAorUaE or Moron nous Jacque C. Morrell. Chicago, lll., alsignorto Universal Oil Products Company, Chicago, lll., a corporation of Delaware Application January 29, 1936,- Serial No. 61,263 1o claims, (cl. 19eloi terparts of normally gaseous olens to produce further quantities of polymerizable gases so that substantially complete utilization of hydrocarbons of'3 and 4 carbon atoms in the production of liquid motorv fuel fractions is accomplished.

In one specific embodiment, the invention comprises the treatment of hydrocarbon gas mixtures comprising lboth paraiiin and olenn hydrocarbons with solld'phosphoric acid catalysts in stages` characterized by variable temperaturas. g.l of the order of '15 F. to 500 F. and pressure and cata c relationships to selectively and successivelypoiymerize and separate the oleiins in the orderoi' their reactivity, following which the re- .sldual paraiiinic hydrocarbons are catalytically dehydrogenated, the hydrogen separated and the olens recycled to catalytic polymerization..

In a preferred embodiment, the process is directed to the treatment of the hydrocarbon gas mixtures produced incidental to oil cracking operations, particularly those containing "relatively high percentages oi! 3 and 4 carbon atom hydrocarbons such as stabilizer reiiuxes. The gases treated may also contain 2 carbon atom hydrocarbons.

I have found that by utilizing certain types of solid phosphoric acid catalysts which will be later described more in detail thatv the oleiinspresent ,in hydrocarbon gas mixtures can be selectively and successively polymerized and have particularly determined that this. separation is best effected while Vvarying the teemperatures at which the olens are contacted withthe solid catalysts over a considerable range. it to be both possible and practical to catalytically I have further found dehydrogenate residual paralnlc gases which remain after the polymerization oi the oleflns in cracked gas mixturesso that substantially all of the 3 and 4,carbon atom hydrocarbons are utilized as a source of good motor fuel stock.

The polymerlzing` catalysts which are used in the present connection areof a special and unique character and warrant detailed description, asthey are evidently peculiar in their wction. 'Ihey are made generally by mixing an acid of phosphorus, preferably a phosphoric acid such as the ortho and the pyro acid, withA a substantially unreactive and generally siliceous adsorbent until a paste is obtained, this 'paste being then calcined to 'produce a solid cake, which is ground and sized to produce catalyst granules. It has been found in the case of highly adsorbent materials, such as kieselguhr, that primary comphorus is the major constituent by weight. Thus a stiff paste is produced when parts of commercial ortho-phosphoric acid is mixed at` ordinary temperatures with 20 parts of kieselguhr. Conversely, relatively dry mixes result when about 30 parts of this acid is mixed with 70 parts by weight of the adsorbent. By incorporating varying quantities of phosphoric acid with these adsorbents, catalyst masses are produced which have varying polymerizing eiectiveness which may be due to the variation in the actual contact surface of the acid which is exposed during service.

By controlling the proportions of adsorbent and acid andalso the temperature employed in the drying or calcining step, granulary catalyst composites may be produced which vary both in the percentage of the acidic component and in the strength of said component. Thus for the.

polymerization of such readily polymerizable compoundsas iso-butylene catalysts may be utilized which have been produced by merely mixing commercial orthophosphoric acid of approximately concentration with a siliceous and finely divided adsorbent material and drying at temperatures of approximately 250 F. to 300 F., which operation if conducted for periods of time which vary somewhat with the amount of acid present in the mix, ultimately yields solid catalysts which contain orthophosphorio acid as their essential constituent.

When a catalyst composite comprising an acid approximating the pyro acid in composition as the essential active ingredient is desired, and the ortho acid has been used in the primary mixtures, themost effective catalysts are produced when the pasty mixtures are heated at temperatures from approximately 400 to 600 F. for a considerable period of time, usually from 40 to 60 hours. During this heating water is evolved and analysis shows that the remaining acid has a composition closely approaching that ofthe pyro acid. Advantages are frequently gained in utilizing the higher temperatures and also in starting with the pyro acid. When using this acid in primary mixes temperatures of from approximately 310 to 360 F. are used to insure proper iluidity. With eillcient mixing devices the time required for producing uniform distribution is lowered considerably, frequently only 5 minutes being required. If dehydration is found to have taken Place to too great an extent so that the polymerizing e'e'ctiveness is reduced (as shown by small scale tests) the particles may be contacted with superheated steam at temperatures within the approximate range of 400 to 600 F. to produce the catalytic acid of optimum composition.

- A feature of the present invention resides in the employment of ordinarily liquid phosphoric acids as polymerizing catalysts in substantially solid form, this being accomplished by the alternative use of a number of diiferent adsorbent carrying materials which vary somewhat in their adsorptive capacity and also in their chemical and physical properties and their influence upon the catalytic ei'fect of the mixtures. 'Ihe materials which may be employed are divisible roughly into two classes. The iirst class comprises mate'- rials of a predominately siliceous character and includes diatomaceous earth, kieselguhr and articially prepared porous silicas such as, for example; Sil-O-Cel. In the case of naturally occurring diatoms it is believed that they sometimes contain minor amounts of highly active aluminum oxide which in some instances seems to con'- tribute to the total catalytic effect of the solid catalyst. 'I'his active material is not present in the artificially prepared forms of silica.

.The second class of materials which may be employed either alone or in conjunction with the irst class (and with certain other optional ingredients to be later described) comprises generally certain members of the class of aluminum silicates and includes such naturally occurring substances as the various fullers earths and l0 this general class are characterized by a high 20 adsorptive capacity which is particularly in evidence in making up the present type of phosphoric acid catalysts, and they may also contain traces of active ingredients which assist in producing the desired polymerizing eiiects. Again each substance which may be used alternatively will exert its own speciic iniluence which will not necessarily be identical with that of the other members of the class.

To assist in developing the character of the i present invention the attached drawing has been' provided which shows diagrammatically in general side elevation and by the use of conventional gures an arrangement oi' apparatus in which thevprocess may be conducted.

Referring to the drawing olefin-containing hydrocarbon gas mixtures such as, for example, those produced as an overhead product in the stabilization of cracked naphthas may be introduced under moderate superatmospheric pressure of .the order of 100-300 lbs. per square inch by way of line I containing control valve 2. A primary heater has not been indicated in the drawing though in practical operation this will usually vbe necessary to control the temperature,

of the gasesv entering the rst catalytic treater.

`The gas mixtures thus admitted are passed in series through a number of catalytic treaters in which conditions of time, temperature and catalytic activity may be separately or collectively increased to produce progressively increasing severity of treating conditions so that the more readily polymeriza'bleolenns are first polymerized and those more resistant to polymerizing influenoes are converted to liquids in the succeeding stages. Preferably there is intermediate cooling and condensation of polymers between stages followedy by reheating of the gases and their further contacting with the preferred catalysts.

Treater I is indicated as the iirst member of a series and contains a mass of granular catalyst I supported upon a perforated false bottom I.

the gas mixture passing downwardly therewhich is one of the heavier constituents of olefincontaining gas mixtures is rapidly polymerized at'temperatures as low as 70 F. so that it may be removed from mixtures without affecting pro- .pylene at all, while the normal butenes are affectthrough.. I have determined that isobutylene a5 thedifierent olenns-therein contained.- A factor 7l greater than that corresponding to a vaporphase by utilizing temperatures below a given point to! first cause the polymerization of thejisobutylene aua-iov influencing the greater rate of polymer'isation of may be partly in liquidphasewhen suilicient pressure is used and are therefore' in contact with the catalyst for a' period of time much operation at temperaturesabove 'their critical temperatures. Later examples will indicate the relative rates of polymerizationl of isobuty'lene and the normal butylenes under temperature conditions at which propylene is substantially unaffected. I

Under the normally low temperatures employedl in the first treater of a series of the prescrit` character substantially all of the -liquidpolyn mers produced will condense in the portion of the treater below the catalyst mass -and may' l tepassed alongl with incondensibie gases through a line 8 containing a control valve 1'- through a,- 'cooler 8 and thence through a line l containing a control valve i to a receiver II.'- 'The liquid polymers formed in this primary stage will coni sist principally of the dimer of isobutylene which hasl been found to`be hydrogenatable 'to iso -octane or 2,2,4-'trimethylpentane 'Some mixed polymerization of' isobutylene with n-a .and butylenes will occur but to a lesser extent. The

polymers may be drawn oi! though aline i2 containing a control valve Il. i

'I'he residual gases in receiver il which comprise the majority ofthe n-butenes, propylene and ethylene along with their paramnic counterf,l

parts are passed through line -i4 containing control valvel i5 to a pump or compressor Il which discharges themvthrough line l1 containing control valve I8 and through an intermediate heatf ing element I 5 disposed-to receive heat from a furnace 20. f

We have found that it is possible and practical present in olefin-containing. mixtures Av so that a large amount oi' the polymer di-isobutylene which hydrogenates to 2,2.4k-trlmethyl pentaney is: formed and further that at slightly -elevated temperature above this point and after-the -removal this direct type of polymerization'. thehe'xt stage in the polymerization reactions is represented by the condensation of residual 'isobutylenemolecules with molecules of normal butcnesfth mixed' polymers formed in this manner yielding 2.2.3- trimethylpentane on hydrogenation. Since the mechanism of the reactions leading ultimately to polymer formation when employingj pl'iosphorio acid as a catalyst is evidentlythe primary formation of esters, the minimum temperature utiliz-v o.

able to form polymers from a given olefin'will be in general Athat corresponding to the stability of the ester. v

The average conditions for causing further mixed polymerization reactions between iso and n-butylenes in the second stage of a process of the-present character are generally temperatures within the approximate range of 150-250 F.

when employing the preferred type of solid phos phoric acid catalyst.` Y Obviously if the amount of isobutylene remaining vunpolymerized after the in the final stage above 400 F. These stages may. however, overlap.

Thus -a gas mixture after the polymerization of a substantlalportion "of the original isobutyiene content may be brought to a point within this temperature range and passed by way'of line 2i containing control valve 22 through a second stationary mass of granular catalyst 24 ysupported on a perforated vplate 25 in a secondary treater 22, and the polymers formed then liquefied by cooling and condensation. In this intermediate stage the liquid polymers may condense as in the first stage if they are present in sufficient concentration and they will then pass through aline 26 containing control valve 21, througha cooler `20 and thence through a line 2l containing control valve I0 to a receiver 3|. The liquid polymers from the second stage which will contain a high percentage of mixed octylenes which are hydrogenatable to 2,2,3-trimethy1- pentane will be remoyed by way of draw line 32 containing control valve 33 to suitable storage.

,- The :residual gases `which will be substantially .fre' from 4 -carhorir atom oleflns and contain only propyleneand ethylene as representatives'of this 'series will pass through line 34 containing control valve l5 to a second gas pump I5 and be discharged through line 51 containing control valve n through a heating element 39 arranged in a furnace setting 40.

l The temperatures employed in the nal catalytic treater which functions to polymlerize residof V40G-500" F. and as before the entering gases are heated to a suitable temperature within this range and passed through line 4 i containing conof a considerable portion of the isobutylene ,by

trol valve 42 downwardly through a granular `catalytic mass 44 supported upon a perforated false bottom 45 in a treater 43.

After the final stage of polymerization for the removal of propylene as a mixture of dimers and trimers thereof and possibly 'some mixed poly--V merswlth ethylene and ,any residual butylenes, the total gas mixture is passed by way of a line 45 containing control valve 41 to a cooler 48 to condense the polymers and the'total products are then passed by way of line 49 containing control valve 50 to a receiver 5i which has a liquid vdraw line 52 containing a control valve 5l. The

gas mixture remaining at this point will contain 'substantially' no olens other-4 than ethylene and relatively large percentages of 3 and 4 carbon atom paraln hydrocarbons. ln order to produce more olens for polymerization this gas mixture is passed from the receiver by way of line 54 containing control valve 55 to a gas pump 56 and is discharged by wayof line 51 containing control valve 58 through a heating element 59 disposed to receive heat from a furnace 60. The optimum temperature for catalytically dehydrogenating the 3 and 4-carbon atom paraflln hydrocarbons comprising propane, isobutane and n-butane is commonly Within the range of 900950 F. depending upon the concentration of ual propylene after removal of the 4 -carbon these hydrocarbons in the gas mixture and the particular catalyst employed. `The pressure is substantially atmospheric or at most only sufiiciently superatmospheric to cause flow through the dehydrogenat-or and the cooler following. 'I'he heated gas mixture passes through line 8| containing control valve 62 and enters a chamber 83 containing a mass of dehydrogenating catalyst 6l supported upon a perforated plate 65.

The catalysts which have been found most suitable for selectively dehydrogenating normally .paramnic gases to produce their olefinic counterparts are those which comprise refractory oxides kand certain silicates as base material supporting minor additions of alkali and heavy metal salts. The preferred oxides are those of magnesium produced by calciningvthe normal magnesite at temperatures of approximately 1600 F. and

`aluminum oxide produced by a similar calcinaemploy compounds of the alkaline earth metals.v Active catalytic masses have been prepared by v properly adding salts of the following acids as promoters: chromlc, boric, carbonio, molybdic,

.pertitanic, permanganic, aluminio, phosphoric,

vand chemical properties of the material, particularly with its solubility in water. The numerous alternative catalysts which may be thus prepared! have distinct and peculiar activity when employed in dehydrogenating parafhnic gases and are not exactly equivalent in their action although substantially all possess sufficient catalyzing power *to warrant their use in practice. The selection 'of' any particular alternative catalyst will be determined by cost considerations and the efficiency of the selected catalyst upon the dehydrogenating reaction being dealt with.

According to one alternative mode of operation the gas mixture from the catalytic dehydrogenator which will contain considerable percentages of hydrogen, methane, ethane and ethylene is cooled suiiiclently so that there is a 'separation as liquid of the hydrocarbons containing three or more carbon atoms while the fixed gases mentioned are withdrawn and their diluent effect upon subsequent treatment of the olefins is eliminated. Thus the hot gas 'mixture from dehydrogenating element 63 may pass through a line 66 containing control valve 61 through a cooler 88, the cooled products comprising both liquids and gases following line 69 containing control valve 1li to receiver 1I, and the fixed gases meptioned being then withdrawn by way of vent line 12 containing control valve 13.

3 and 1 -carbon atom olefins and such portions of their corresponding paraflins which have not been dehydrogenated will then be passed in liquid phase through line 1l containing control valve 15 to recirculating pump 16 which discharges the highly oleinic liquids through a line 11 containing control valve 1l back to line I. 'I'hese products may need some further heating to bring them to the proper temperature for the primary step of polymerization and this heat may be picked up from the gases in line I by direct heat exchange.

It will be obvious from the foregoing general description that the present process permits the practically complete utilization of all 3 and 4- carbon atom hydrocarbons present in hydrocarbon gas mixtures such as those released from the receivers of oil cracking plants or as stabilizer reflux formed from the primary gasoline-containing distillates. These hydrocarbons are treated in such a way that three separate polymer products are produced which in general will have a decreasing antiknock value in the order of their production. The process thus permits a control in the production of different types of blending material for improving the antiknock value of inferior motor fuel fractions.

The following example is given to illustrate the general character of the results obtainable by the present process though it is not given with the intent of correspondingly limiting the scope of the invention.

-A cracked stabilizer reflux was treated which had the following approximate composition: Ethylene 4%, ethane 5%. propylene 20%, propane /30%, isobutylene 8%, n-butylenes 12%, and

butanes 21%.

An eilcient polymerizing catalyst was employed which had been manufactured by adding approximately 65% by weight of pyrophosphoric acid to kieselguhr followed by thorough mixing at a temperature of 320 F., further heating at 608 F. to produce a cake and grinding and sizing to produce catalyst granules of approximately 6-20 mesh. A mass of these granules was used as a filler in vertical treating towers which were employed in series to remove first the major portion of the isobutylene, then the butenes and lastly the propylene.

For the selective polymerization of the isobutylene content the stabilizer reflux which was substantially in liquid phase was passed downwardly through the first treating tower at normal atmospheric temperatures of approximately 70 F. at a pressure of about 200 pounds per square inch. 'I'he liquid resulting was stabilized by heating to approximately 150 F. which vaporized substantially all of the residual unpolymerized three and four-carbon atom olefins and left principally diisobutylene polymer. The gases were passed through a second treater at the temperature at which they were produced and this second catalyst contact polymerized substantially all of the residual four-carbon atom olefins to make a mixture of octenes.

Following the second stage the liquid polymers were separated and the gas mixture which then contained substantially only propylene as its oleflnic constituent was heated to a temperature of 450 F. and passed through a third bed of catalyst to polymerize the propylene to dimeric and trimeric forms.

The residual gases from the stabilization of the propylene polymers were subjected to dehydrogenation at a temperature of 932 F. and substantially atmospheric pressure using as a catalyst a granular magnesium oxide supporting successive deposits of lead chromate and zinc sulfate, the total weight of the promoting substances being about 5% of. the total weight of the composite. The dehydrogenated parains were collected as liquids by appropriate cooling and compression whilethe lighter iixed gases were removed.

By the foregoing procedure substantially all of the 3- and 4carbon atom hydrocarbons both parafnic and oleiinic were converted into liquids boiling within the gasoline range since the propane and butanes were each converted to a substantial degree into their corresponding olens in the catalytic dehydrogenating step. The following table shows the average yields and octane numbers of the olefinic polymers produced continuously in the three stages.

Stage V Gals. M. cu. it.. 0. N.. motor No. oigas v method 1 `2.o sa 2 6.0 82 3 10.0 so

by secondary reactions involving release of 'hydrogen and hydrogenation of a certain lportion of the low boiling olefins. 'Ihe exact character of these reactions is dii'licult to follow on an analytical basis.

The lnovelty and utility of the present invention can be seen from the foregoing specification and example although neither section is to be construed as unduly limiting its generallybroad scope.

I claim as my invention: -1

1. A process for the conversion of hydrocarbon gases comprising paraiiin hydrocarbons and substantial amounts of propylene and butylenes into liquid hydrocarbons, which comprises subjecting the hydrocarbon gas to the action of a polymerizing catalyst' at temperatures o1 the order of 70 to 200 F. under sumcient pressure to maintain a substantial portion thereof. in liquid phase to.

polymerize and convert the butylenes into liquid olenic hydrocarbons, separating the resulting liquid olefins from the unconverted gaseous hydrocarbons, subjecting the latter to the action of a polymerizing catalyst at a temperature of from 200 to 500 F. to polymerize and convert the propylene into liquid olens, separating the resulting olens from the unconverted residual gases, subjecting the. latter containing the paraffin hydrocarbons to the action of a dehydrogenating catalyst at a dehydrogenating temperature to convert the paramn hydrocarbons into gaseous oletins, separating resultant 3 and 4 carbon atom oleilns as liquid from the gaseous dehydrogenaa tion products of kless than 3 carbon atoms returning the thus separated olens in liquid form to the first-mentioned polymerizing stage for further polymerizing treatment, and recovering the polymerized liquid hydrocarbons produced in each polymerizing stage.

2. A process such as claimed in claim l wherein the polymerizing catalysts used comprise essentially a phosphoric acid. v

3. A process such as claimed in claim l wherein the polymerizing catalysts used comprise essentially an acid of phosphorus.

4. A process such as claimed in claim 1 wherein the dehydrogenating catalyst comprises essentially aluminum oxide and a promoter catalyst.

5. A. process for the conversion of hydrocarbon gases comprising paraffin hydrocarbons and subthehydrocarbon gas to the action of a polymeriz.

ing catalyst comprising essentially a phosphoric acid at temperatures of the order of 'l0 to 200 F. and under sufcient superatmospheric pressure to maintain a substantial portion thereof in liquid phase to polymerize and convert the butylenes into liquid olens, separating the resulting liquid olefins from the gaseous hydrocarbons, subjecting the latter to the action of a polymerizing catalyst comprising essentially a phosphoric acid at temperatures of the order of 200 to 500 F. under superatmospheric pressure to polymerize and convert the propylene into liquid olens, separating the resulting liquid oleilns from the residual gases, subjecting the latter containing the paraiiin hydrocarbons to the action of a dehydrogenating catalyst comprising essentially aluminum oxide and a promoter, at a dehydrogenating temperature, to convert the paraffin hydrocarbons into gaseous oleiins, separating resultant 3 and 4 carbon atom olens as liquid from the gaseous dehydrogenation products of less than 3 carbon atoms and returning the thus separated oleiins in liquid form to the irst-mentioned polymerizing stage for further polymerizing treatment.

6. A process for the treatment of hydrocarbon gases to convert tlie same into liquid hydrocarbons which comprises, subjecting the hydrocarbon gases in several stages to the action of a polymerizing agent to selectively polymerize the 4-, 3- and 2-carbon atom olens contained therein by subjecting the hydrocarbon gases under sufiicient pressure to maintain a substantial por- 'tion thereof in liquid phase to the action of a F., lseparating thetliquid hydrocarbons from the residual gases comprising essentially paraiiin hydrocarbonsLsubjecting the residual gases to the action of a dehydrogenating catalyst at a dehydrogenating temperature to convert the parailin hydrocarbons into olen hydrocarbons, separating resultant 3 and 4 carbon atom olens as liquid from the gaseous dehydrogenation products of less than 3 carbon atoms returning thus-separated olen hydrocarbons in liquid form to the first-mentioned polymerizing stage for further polymerizing treatment, and recovering the polymerized liquid hydrocarbons produced in each of the polymerizing stages.

'7. A process such as claimed in claim 6 Wherein the dehydrogenating catalyst comprises essentially aluminum oxide and a promoter.

8. A process for the treatment of hydrocarbon gases to convert the same into liquid hydrocarbons which comprises, subjectingl the hydrocarbongases in several stages to theaction of a polymerizing agent to selectively polymerize'the 4, 3- and 2-carbon atom olefins contained therein by subjecting the hydrocarbon gases under sufficient pressure to maintain a substantial portion thereof in liquid phase to the action of a polymerizing catalyst comprising essentially a solid phosphoric acid at a temperature of from 'I0 to 200 F. in the rst stage of the process, sepa.- rating the liquid and gaseous hydrocarbons, subjecting the gaseous hydrocarbons to the action `of a polymerizing catalyst comprising essentially a solid phosphoric acid in the second stage of the process at a. temperature of from 200 to 400 F., separating the liquid hydrocarbons from the gaseous hydrocarbons, subjecting the resulting gaseous hydrocarbons to the action of a polymerizing catalyst comprising essentially a solid phosphoric acid at a temperature above 400.'F., separating the liquid hydrocarbons from the residual gases comprising essentially lparailin hydrocarbons, subjecting the residual gases to the action of a dehydrogenating catalyst at a dehydrogenating temperature to convert the paraffin hydrocarbons into olefin hydrocarbons, separating resultant 3 and 4 carb n atom oleiins as liquid from the gaseous dehy rogenation products of less than 3 carbon atoms, returning the thus sepa-` rated olefin hydrocarbons in liquid form to the rst-mentioned polymerizingvstage' for further polymerizing treatment. and' recovering the polymerized liquid hydrocarbons produced in each of the polymerizing stages.

9. A process for producing normally` liquid hydrocarbons from a mixture of 3 and 4 carbon atomolens and paraillns which comprises subjecting the mixture to catalytic polymerization under sumcient pressure to maintain a substantial portion thereof in liquid phase, separating resulting oleiin polymers from the unconverted paraiiins, dehydrogenating the separated parafflns to produce 3 and 4 carbon atom oleilns therefrom, separating the latter as liquid from the gaseous dehydrogenation products of less than 3 carbon atoms, and supplying the 3 and 4 carbon atom olens in liquid .form to the polymerizing step.

10. A process 4ior producing normally liquid hydrocarbons from a normally gaseous mixture of more than 2 carbon atom hydrocarbons, ln-

JACQUE C. MORREIL. 

